I also agree that an ingame mail or announcement of some kind would be a good move, and definitely better than finding out about this from a 3rd party, or even worse after the fact... It's highly possible you will get additional sales if more people knew. On that same subject I appreciate that you at least confirmed the rumor here, but this does bring up many questions that others have expressed. I know you have stated that you can't share more at this time, but you can definitely appreciate our concern.
Lastly I'd like to add that while Sasuske is a fantastic ninja and it'll be a real shame for all those that miss out on him, I'd like to at least caution people before they spend a ton to get Shikamaru. After getting him in the last event I've done quite a bit of testing and unfortunately he doesn't seem to function all the time with "Secret Jutsu" ninjas, so please just be aware of this in case it never gets fixed.